Copyright law is designed to protect the authors of creative works, such as novels, songs and movies, from the unauthorized reproduction or other use of their created material. Ideas may not be copyrighted in the absence of a work that expresses them. An idea for a book cannot be copyrighted, but the book itself may be. Neither does copyright protect words, phrases or slogans, though they may sometimes be registered as trademarks.
Write the book. Under United States copyright law creation of the a book or any other work automatically establishes copyright. No other action of the author is required, but some other actions may be beneficial.
File copyright registration. Registering a work with the United States Copyright Office fixes a creation date that can document its protected existence before any intellectual infringement occurs. The registration date is determined by when the work is received in the Copyright Office.
Affix a "Notice of Copyright" to the book or other visually perceptible work. The letter "c" enclosed in a circle, with the year the work was created and the author's name constitute a notice of copyright in the United States.
Publish and distribute the book. While no longer required by United States copyright law secure copyright, publication also establishes an author's ownership of any work.